This work is designed to extend our knowledge of the communicative and symbolic behaviors that facilitate the initial acquisition of augmentative and alternative communication (AAC) skills in young children at risk for poor vocal expressive communication. Research in normal language development has shown that early communicative behaviors, such as symbolic gestures and joint attention routines, predict the rate and extent of later language development. Access to AAC has been demonstrated as a means to acquire some of the necessary prelinguistic and cognitive skills that are essential for language development, but AAC is ratrely implemented before the age of 3-4 years. There is a widespread clinical need for better early identification of children who need intensive therapy to avoid the language delays associated with poor access to expressive communication. Existing data do not provide adequate information about either the expected language progress of young AAC users or the communicative characteristics that indicate concern for later development. Therefore, the current project will analyze the process of acquiring AAC skills in parallel with prelinguistic communicative behaviors for children with severe physical disabilities. The proposed research project will address three specific aims by: (a) measuring communicative and symbolic behavior development in young children who require AAC intervention due to severe physical impairments, (b) examining predictors of the early symbolic use of AAC, and (c) testing the validity of hroup data at predicting AAC development for individual children. Longitudinal data will be collected from children beginning at the ages in which normally developing children begin to display communicative behaviors that precede symbolic development, and ceasing when children display criterion levels of AAC skills. Data will be analyzed and compared for the following factors: communicative and symbolic behaviors during struyctured and unstructured tasks, interaction style and joint attention routines during free play, standardized tests of language, cognition, and motor development, and AAC skills at using switch and voice output technology to convey different communicative functions in structured interactions. The outcome of this analysis will then be used to assess precursors to successful AAC use and to develop and test predictions for early identification of subjects who do not demonstrate criterion level AAC skills. It is predicted that early communicative and interactional patterns will distinguish children who develop criterion levels of AAC competence from children who do not show functional AAC contro by the end of the study. The resulting benefits for health professionals will be better criteria for early referral for AAC services, clearer identification of critical goals for efficacious treatment, and more efficient application of AAC assessment and treatment criteria for children who have the greatest need for those services.